A person's inner ear includes the labyrinth, a delicate memberous system of fluid passages that includes both the cochlea (which is part of the auditory system), and the vestibular system (which provides part of the sense of balance). The eyes also provide signals used for balance, as do joint and muscle receptors and the cerebellum. The brain, specifically the vestibular nuclear complex, receives and analyzes the information from these systems, and generates signals that control a person's balance.
Each inner-ear includes three semicircular canals and a vestibule, the region where the semicircular canals converge, and which is close to the cochlea (the hearing organ). The vestibular system also works with the visual system to keep objects in focus when the head is moving.
Interference with, or infection, of the labyrinth can result in a syndrome of ailments called labyrinthitis. The symptoms of labyrinthitis include temporary nausea, disorientation, vertigo, and dizziness. Labyrinthitis can be caused by viral infections, bacterial infections, physical blockage of the inner ear, or due to decompression sickness.
Some people lose vestibular hair cells or suffer from balance and dizziness problems that are not readily treatable through therapy and/or drugs. These conditions can be very debilitating, since the affected person must remain still to minimize unpleasant dizziness or feeling continuously “seasick.” The condition can also affect their ability to walk or keep their balance in general.
The semicircular canals in the inner ear form three loops that are fluid filled and sense rotation of a person.
Otoliths (earstones) are small particles composed of calcium carbonate supported in a gelatinous matrix in the viscous fluid of the saccule and utricle (the utricle is located in the vestibule, between the semicircular canals and the cochlea within a swelling adjacent to the semicircular canals, and the saccule is closer to the cochlea). The inertia of these small particles (sometimes referred to as stones or crystals) causes them to stimulate hair cells differently when the head moves. The hair cells send signals down sensory nerve fibers via the vestibulocochlear cranial nerve (CN VIII), which are interpreted by the brain as motion. The vestibular nucleus coordinates inputs from the muscles responsible for posture via the spinal cord, information on control, balance, and movements via the cerebellum, and head and neck movements via cranial nerves III, IV, and VI.
The saccule and utricle together make the otolith organs. They are sensitive to gravity and linear acceleration. Because of their orientation in the head, the utricle is sensitive to a change in horizontal movement, and the saccule gives information about vertical acceleration (such as when in an elevator). The otolith organs also provide information to the brain orientation of the head, such as being in a vertical position or prone position, or being face-up or face-down.
When the head is in a normal upright position, the otolith presses on the sensory hair cell receptors. This pushes the hair cell processes down and prevents them from moving side to side. However, when the head is tilted, the pull of gravity on statoconia shift the hair cell processes to the side, distorting them and sending a message to the central nervous system that the head is no longer level but now tilted. The motion sensation from the otoliths is involved in a large number of reflexes. Damage to the otoliths or their central connections can impair ocular and body stabilization.
U.S. Pat. No. 7,225,028 issued to Della Santina et al. on May 29, 2007, and titled “Dual Cochlear/Vestibular Stimulator with Control Signals Derived from Motion and Speech Signals”, is incorporated herein by reference. Della Santina et al. describe a system for treating patients affected both by hearing loss and by balance disorders related to vestibular hypofunction and/or malfunction, which includes sensors of sound and head movement, processing circuitry, a power source, and an implantable electrical stimulator capable of stimulating areas of the cochlea and areas of the vestibular system.
U.S. Patent Application Publication Number US 2007/0261127 A1 filed Jul. 24, 2006 by Edward S. Boyden and Karl Deisseroth, titled “LIGHT-ACTIVATED CATION CHANNEL AND USES THEREOF”; U.S. Patent Application Publication Number US 2007/0054319 A1 filed Jul. 24, 2006 by Edward S. Boyden and Karl Deisseroth, titled “LIGHT-ACTIVATED CATION CHANNEL AND USES THEREOF” filed Jul. 24, 2006; and U.S. Patent Application Publication Number US 2007/0053996 A1 filed Jul. 24, 2006 by Edward S. Boyden and Karl Deisseroth, titled “LIGHT-ACTIVATED CATION CHANNEL AND USES THEREOF” are all incorporated herein by reference. These describe compositions and methods for light-activated cation channel proteins and their uses within cell membranes and subcellular regions. They describe proteins, nucleic acids, vectors and methods for genetically targeted expression of light-activated cation channels to specific cells or defined cell populations. In particular the description provides millisecond-timescale temporal control of cation channels using moderate light intensities in cells, cell lines, transgenic animals, and humans. The descriptions provide for optically generating electrical spikes in nerve cells and other excitable cells useful for driving neuronal networks, drug screening, and therapy.
U.S. Pat. No. 6,748,275 issued to Lattner et al. on Jun. 8, 2004, and titled “Vestibular Stimulation System and Method” (herein “Lattner et al. '275 patent”), is incorporated herein by reference. Lattner et al. '275 patent describes an apparatus and method in which the portions of the labyrinth associated with the labyrinthine sense and/or the nerves associated therewith are stimulated to perform at least one of the following functions: augment or control a patient's respiratory function, open the patient's airway, induce sleep, and/or counteract vertigo.
U.S. Pat. No. 7,004,645 issued to Lemoff et al. on Feb. 28, 2006, and titled “VCSEL array configuration for a parallel WDM transmitter”, is incorporated herein by reference. Lemoff et al. describe VCSEL array configurations. WDM is wavelength-division multiplexing. Transmitters that use several wavelengths of VCSELs are built up out of multiple die (e.g., ones having two-dimensional single-wavelength monolithic VCSEL arrays) to avoid the difficulty of manufacturing monolithic arrays of VCSELs with different optical wavelengths. VCSEL configurations are laid out to insure that VCSELs of different wavelengths that destined for the same waveguide are close together.
U.S. Pat. No. 7,116,886 issued to Colgan et al. on Oct. 3, 2006, and titled “Devices and methods for side-coupling optical fibers to optoelectronic components”, is incorporated herein by reference. Colgan et al. describe optical devices and methods for mounting optical fibers and for side-coupling light between optical fibers and VCSEL arrays using a modified silicon V-groove, or silicon V-groove array, wherein V-grooves, which are designed for precisely aligning/spacing optical fibers, are “recessed” below the surface of the silicon. Optical fibers can be recessed below the surface of the silicon substrate such that a precisely controlled portion of the cladding layer extending above the silicon surface can be removed (lapped). With the cladding layer removed, the separation between the fiber core(s) and optoelectronic device(s) can be reduced resulting in improved optical coupling when the optical fiber silicon array is connected to, e.g., a VCSEL array.
U.S. Pat. No. 7,031,363 issued to Biard et al. on Apr. 18, 2006, and titled “Long wavelength VCSEL device processing”, is incorporated herein by reference. Biard et al. describe a process for making a laser structure such as a vertical cavity surface emitting laser (VCSEL). The VCSEL designs described include those applicable to the 1200 to 1800 nm wavelength range
U.S. Pat. No. 6,546,291 issued to Merfeld et al. on Apr. 8, 2003, and titled “Balance Prosthesis”, is incorporated herein by reference. Merfeld et al. describe a wearable balance prosthesis that provides information indicative of a wearer's spatial orientation. The balance prosthesis includes a motion-sensing system to be worn by the wearer and a signal processor in communication with the motion-sensing system. The signal processor provides an orientation signal to an encoder. The encoder generates a feedback signal on the basis of the estimate of the spatial orientation provides that signal to a stimulator coupled to the wearer's nervous system.
Vestibular problems in the inner ear, the semicircular canal organs or the otolith organs can cause very debilitating conditions, including dizziness and vertigo. Improved apparatus and methods are needed to diagnose and/or treat various problems in animals, including vestibular problems.